The present invention relates to fluid dispensing tool assemblies for evacuating and charging a fluid into a fluid system and of the general type disclosed in U.S. Pat. No. RE34,715 and in U.S. Pat. Nos. RE 34,426 and 4,889,149 which issued to the assignee of the present invention. As disclosed in the '426 and '149 patents, such tool assemblies are commonly used to fill motor vehicle air conditioning and other air conditioning and refrigeration or refrigerant systems by first evacuating the system and then charging or filling the system with a predetermined volume of liquid refrigerant in addition a predetermined volume of lubricating oil for the compressor. Since all of the air in the system is removed during the evacuation cycle, the refrigerant system is filled completely without residual air pockets.
With any such dispensing tool assembly for evacuating and filling a refrigerant system, it is desirable for the tool assembly to be compact and lightweight for convenient maneuvering into small spaces, to be easily and quickly coupled to the refrigerant system, and to be simple in construction with the minimum number of parts. It is also desirable for the tool assembly to have control valves and passages which do not restrict the flow of fluid through the tool assembly during evacuation and filling so that a high fill rate and a short cycle time may be obtained. In addition, the tool assembly should minimize the release of refrigerant into the atmosphere when the tool assembly is removed from the refrigerant system, and have control valves which can be rapidly and pneumatically actuated to provide precision charging and precision repeatability in addition to obtaining a minimum cycle time. While the charging or dispensing tool assemblies disclosed in the above mentioned patents provide some of these desirable features, none of the tool assemblies provide all of the features.